Historical Articles

QUESTION BOX

Readers’ questions
of general interest

Q. 164. What is more advisable to
use for chroming engraving rolls for textile
industries—a vertical or horizontal tank?

A. Rolls or rollers may be
chromium plated in either the vertical or the horizontal position, and
both positions have their advantages and disadvantages.
The advantages
of vertical plating are that the rolls are held stationary in simple racks’ and
that the ends of hollow rollers or shells can be easily sealed to prevent
solution from etching the inside. The disadvantages of vertical plating
are that the
depth of the tank and the headroom above the tank must exceed the length
of the rolls;
and that continuous mechanical or air agitation of the solution is required
to make the temperature of the solution the same at the bottom of the tank
as it
is at the top, so that the lower ends of the rolls will not plate heavier.

The
advantages of horizontal plating are that an ordinary plating tank with’ ordinary
headroom can be used and that no equipment is required to agitate the
solution. The disadvantage of horizontal plating is that a motor-driven
mechanism
is required to keep the rolls continuously oscillating or rotating to’ insure
uniform plate. Maintenance costs of horizontal plating are higher and
more floor space
is required. Most new installations for chromium’ plating engraved
rolls for the textile industries are designed to plate the rolls in the
vertical position.—J.
M. HOSDOWICH.

Q. 165. Do you know of an instrument
that will measure the thickness of a non-magnetic metallic coating such as
molybdenum or copper
on a
non-metallic
such as glass?

A. There is available a gamma radiation
type instrument (name of supplier was furnished) which will measure accurately
in the range
suggested—(0.005
inch differences plotted across a 10-inch scale)—and appears
to be of practical use in this problem.— ANON.

Q. 166. What
is the most modern method for quantity production, to 24 karat
gold flash (electroplate) zinc permanent mold castings?

A. Gold plating of
zinc die castings would involve the same pretreatment as chromium plating
the same item. The item would be polished,
cleaned and then bright copper
and bright nickel plated. After adequate rinsing the work is
ready for gold plating.
The size of the gold solution will depend on the size of the
item and the volume of production. The size of the nickel plating
racks
are
also a factor
if the
item is to be gold plated without reracking. Since the time of
plating for a flash deposit is short (10 to 30 seconds) the tank
is quite
small (40 to
100
gallons). The gold control is low (3 to 5 dwt per gallon). It
is also best to modify the solution by adding small amounts of
base
metals.

The general plating conditions are
140-160° F, 3 to
5 volts, 10 to 30 seconds and no agitation. Such solutions
using constant temperature, constant current
density, automatic timers, duration of plate and ampere-hour
meters for replenishment will give trouble free constant-color
plating. The larger sources of color change
are narrowed down to drag in of nickel and organic contamination.
Relatively small amounts of nickel will pale out the gold color.
Organic contamination will
cause a dead or dull appearance and dark streaks. Such thin
deposits would be best lacquered if the item is to be handled considerably
or exposed to outdoor
corrosion.—EDWARD A. PARKER.

Q. 167. We are interested
in obtaining details on the immersion plating of steel with
cadmium, zinc or tin. We would appreciate
any information
you
could pass
along on plating of this type.

A. Immersion tin coatings on
steel are covered in the report on a recent (1-11-52) Swiss Patent No.
284,092 issued to
Braunschweizer Huttenwerk.
The formulae:
30 g/l stannous chloride
15 g/l cream of tartar with the addition of zinc or
0.35 g/l of stannous chloride and 55 g/l sodium hydroxide

The solution is operated
at or above boiling, in the latter case in an autoclave. In contact with,
e.g., aluminum,
coatings of
0.0001-0.0005 mm are obtained.

Another method for obtaining
immersion coatings of tin on steel would be through the use of a preliminary
copper
plate
on the
steel followed
by
immersion tinning
in the solution of the following composition:

Another method of contact which
was worked out in England is based on immersion of the steel part in
the conventional
sodium
stannate-caustic
soda solution.
When a light alloy contact (2S aluminum wire or
braid) is made with the
steel, plating of the part takes place as the aluminum
dissolves in the solution.
The reports from England on this method have been
encouraging, but one or two people
who have tried it here find that the rate of plating
is much less than reported. Evidently it requires
a bit of
experimenting
to
get the right
conditions
of temperature and solution concentration.—A.
KORBELAK and R. M. MACINTOSH.

The information contained in this site is provided for your review and convenience. It is not intended to provide legal advice with respect to any federal, state, or local regulation.
You should consult with legal counsel and appropriate authorities before interpreting any regulations or undertaking any specific course of action.

Please note that many of the regulatory discussions on STERC refer to federal regulations. In many cases, states or local governments have promulgated relevant rules and standards
that are different and/or more stringent than the federal regulations. Therefore, to assure full compliance, you should investigate and comply with all applicable federal, state and local regulations.